This invention has to do with disk drive suspensions, and more particularly with improved load beams for such suspensions. In a particular aspect, the invention provides a suspension load beam better adapted to current manufacturing methods in which during suspension installation in a disk drive the load beam spring portion may be deflected or bent back, beyond its normal operating range. The bending back, even if as little as 0.02 inch of deflection past the datum line (a line in the plane of the suspension mounting datum or the load beam mounting on the actuator support for the load beam), will affect the gram force exerted by the load beam, lessening it and unpredictably, if the load beam is bent beyond its limit of elastic deformation, and to the point of being plastically deformed.
It has been found that plastic deformation occurs when excessive stress occurs at the locus of bending. Accordingly, in the present invention load beam design is improved to enable the load beam to better distribute stresses encountered during installation in a disk drive. It is an object, therefore, of the invention to provide an improved disk drive suspension load beam. In a more particular aspect the invention provides a modified perimeter contour for a load beam in which the radius between the load beam spring portion and the load beam elongated beam portion is increased as much as twice to fivefold or more to enable distribution of stresses encountered in back bending over a greater area and consequent lowering of the peak stress levels to values at which the spring portion is not plastically deformed.
Accordingly, the invention provides a unitary load beam for a disk drive suspension, the load beam having a spring portion providing predetermined gram force properties to the load beam, the spring portion being normally bent beyond its nominal range in the course of its installation into a disk drive with adverse effect on the spring portion and a lessening of the gram force properties exerted thereby, the load beam having a perimeter and comprising a base portion unitary with the proximate end of the spring portion, and an elongated beam portion wider than and unitary with the distal end of the spring portion, the base portion being adapted to provide a mounting surface for mounting the load beam to an actuator, the junctions of the spring portion and the beam portion at the load beam perimeter having a radius distributing the stress of bending the load beam spring portion beyond its nominal range such that the peak value of the stress force is a value less than that at which plastic deformation of the load beam spring portion occurs.
In this and like embodiments, typically: the load beam is fabricated of stainless steel having a yield strength above about 180,000 psi.; the load beam base portion and the load beam spring portion are of about the same width; the load beam portion is tapered inwardly from its proximate end to its distal end, the beam portion being wider than the load beam spring portion at its widest part, and narrower than the spring portion at its narrowest part; and, the radius of the junctions of the beam portion and the spring portion is at least about 0.004 or 0.008 to 0.010 inch or more.
In a particularly preferred embodiment, the invention provides a unitary load beam for a disk drive suspension, the load beam having a spring portion providing predetermined gram force properties to the load beam, the spring portion being normally bent at least 0.08 inch beyond its nominal range in the course of its installation into a disk drive with adverse effect on the spring portion and a lessening of the gram force properties exerted thereby, the load beam having a perimeter and comprising a base portion unitary with the proximate end of the spring portion, and a relatively wider elongated beam portion unitary with the relatively narrower distal end of the spring portion and having left and right edge rails, the junctions of the spring portion and the beam portion at the load beam perimeter having a radius distributing the stress of bending the load beam spring portion beyond its nominal range to a value within which only elastic deformation and not plastic deformation of the load beam spring portion occurs, whereby the gram force properties of the load beam spring portion are at least 96% retained after being bent 0.08 inch beyond its nominal range.
In this and like embodiments, typically: the load beam is fabricated of stainless steel having a yield strength above about 180,000 psi.; the load beam base portion and the proximate end of the load beam spring portion are of like width; the load beam portion is tapered inwardly from its proximate end to its distal end, the beam portion being wider than the load beam spring portion at its widest part, and narrower than the spring portion at its the distal end; the radius of the junctions of the beam portion and the spring portion is at least about 0.008 inch; and, preferably, the radius of the junctions of the beam portion and the spring portion is about 0.010 inch.